Control mechanism



July 21, 1959 c, HALLER 2,896,052

' CONTROL MECHANISM Filed Dec. 11, 1957 2 Sheets-Sheet 1 FIG].

" INVENTOR CLAYTON L.HALLER QM-T SM.

ATTORNEY July 21, 1959 v C. L HALLER CONTROL MECHANISM Filed Dec. 11, 1957 bime'fol40 52 El 2 Sheets-Sheet 2 4O bimetol FIG.6.

INVENTOR CLAY TON L. HALLER ATTORNEY Uite States Patent CONTROL MECHANISM Clayton L. Haller, Mansfield, Ohio, assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application December 11, 1957, Serial No. 702,045 Claims. (Cl. 200-138) This invention relates to thermostats and to contact assemblies therefor, and has for an object to provide improved apparatus of this character.

In accordance with one embodiment of the present invention, a base-supported bimetal carries at its free end a contact assembly made up of a pair of identical contact carriers which, when interengaged in face-to-face relation, support one, or a pair of, contact plates in a bracket with a single locking tab retaining all of the parts in assembled relation.

Accordingly, another object of the invention is to provide simplified apparatus of this type.

The foregoing and other objects are effected by the invention as will be apparent from the following description and claims taken in connection with the accompanying drawings, forming a part of this application, in which:

Fig. 1 is a plan view of a water heater thermostat constructed in accordance with the present invention;

Fig. 2 is a longitudinal sectional view, taken along the line II of Fig. 1, looking in the direction indicated by the arrows;

Fig. 3 is an exploded perspective view of the contact plates and contact carriers;

Fig. 4 is an exploded view of the contact bracket which supports the contact carriers, together with the tab which retains the carriers assembled in the bracket;

Fig. 5 is a longitudinal sectional view of the contact assembly;

Fig. 6 is a sectional view, taken along the line VIVI of Fig. 5, looking in the direction indicated by the arrows; and

Fig. 7 is a fragmentary longitudinal sectional view of a modified construction for use in a singlecircuit thermostat.

Referring now to the drawings in greater detail, particularly to Figs. 1 and 2, the thermostat assembly shown comprises a thermostat assembly base 10 of sheet metal or other material having good heat transfer characteristics, provided with a supporting wall 11 having parallel side walls 12 integral therewith and terminating in flanges 13 at right angles thereto by which the entire thermostat assembly may be mounted upon a wall or surface of a vessel adapted to contain heated fluid, for example, a domestic water heater (not illustrated).

The supporting wall 11 has a rectangular opening 14 therethrough for unrestricted reception of the contact assembly of Figs. 3, 4, 5 and 6, to be described later.

A contact base 16 of electrically non-conductive mate rial is secured on the supporting wall 11 by suitable means such as the pair of rivets 17. The contact base 16 is provided with a rectangular opening 18 of a size and shape corresponding approximately to that of the supporting wall opening 14, and aligned with the latter, and similarly freely receiving the contact assembly.

A first pair of contact arms 21, each including a pair of 90 degree reverse bends, is secured on the outer surface of the contact base 16, by suitable means such as the rivets 22, with its free ends overlying the opening ice 18 of the contact base. A screw 23, having a contact head 24, is adjustably mounted in the free end portions of both contact arms 21 with the adjustment thereof maintained by a nut 26.

A second pair of similar contact arms 31, each having a pair of 90 degree reverse bends, is secured on the outer surface of the contact base 16 by rivets 32, at the opposite side of the contact base opening 18 from the first pair of contact arms 21. The free ends of th second pair of contact arms 31 extend inwardly through the opening 18 and are provided with contacts 33 underlying the contacts 24 of the first pair of contact arms, in spaced relation thereto.

Each of the four contact arms is provided with a threaded opening 34 overlying slightly a larger opening 35 in the contact base, for reception of conventional terminal connecting screws (not shown).

As best shown in Fig. 2, a conventional bimetal 40, secured to a bimetal support 41, is disposed within the thermostat assembly base 10, parallel to, and midway between, the base side walls 12. A bimetal spring hinge 42 mounts the bimetal support 41, and hence the bimetal 40, on the inner surface of the thermostat assembly base supporting wall 11 near the end thereof most distant from the opening 14 therethrough. The free end of the bimetal 40 is aligned approximately with the center of the opening 14 in the supporting Wall 11.

Mounted on the free end portion of the bimetal and extending into the space defined by the aligned supporting Wall opening 14 and contact base opening 18 is the contact assembly 50, shown in detail in Figs. 3, 4, 5 and 6, to which reference is now made.

A U-shaped contact bracket 51, of plastic or other non,- electrically-conductive material, is secured to the free end portion of the bimetal 40, as at 52. Leg 53 of the bracket is provided, near its free end, with an opening 54 therethrough, while the other leg 55 is slotted at its free end, as at 56, both for reception of stub shafts on a pair of contact carriers 57. V

The two contact carriers 57 are identical and are moulded of plastic or other non-electrically-conductive material. Each carrier 57 comprises an elongated body portion 58 of rectangular cross section having a lateral extension 59 from one side 60 of the body portion and at one end thereof, and a projection 61 from an adjacent side of the body member, but at the other end thereof relative to extension 59. The projection 61 also extends laterally beyond the first mentioned side 60 of the body portion, as at 62. v

A pair of spaced separating lugs 63 and 64 also proifit t from side 60 of the body portion 58, the lug 63 being located at the corner formed by the side 60 and the lateral extension 59, and the lug 64 being located on that half of the side 60 which is remote from the lug 63. Both lugs 63 and 64 are the same thickness and are centered on the longitudinal center line of the side 60, with the result that the spacings of the lugs from the two sides of the body portion 58 which are adjacent the side 60 are the same. i

The body portion 58 also has cast integral therewith a pair of parallel bars 66 and 67 extending laterally at right angles to the body portion in the same direction as the separating lugs 63 and 64 and spaced apart by the thickness of the body portion on which they are formed. The bar 66 is approximately twice the length of the bar 67, and the two are so proportioned that when two contact carriers 57 are placed against each other in face-tofrom the side thereof opposite side 60 and centered on the plane containing the meeting faces of the two arms 66 when two contact carriers are assembled.

When a pair of carriers is assembled in a contact bracket 51, one stub shaft 68 is disposed in the opening 54 of bracket lug 53 and the other stub shaft is positioned in the slot 56 of bracket lug 55 (Fig. 5).

A pair of flat rectangular contact plates 70, preferably silver-surfaced, is retained between the pair of contact carriers 57, being separated by the two pairs of lugs 63 and 64, and restrained against movement in its plane by the lateral extensions 59 and the body portions 58, and against movement normal to its plane by the projections 62 and the bars 66 and 67. I

The two contact carriers 57 and their pair of contact plates 70 are retained assembled in the contact bracket 51 by a simple locking tab 71, one terminal portion of which overlies the stub shaft 68 in the slot 56 and the other terminal portion of which 'is reversely bent, as at 72, into a recess 73 in the bottom of bracket lug 55, as clearly illustrated in Fig. 5. As clearly shown in Figs. 3 and 6, the top and bottom surfaces of the stub shafts 68 are curved, so that the contact plates 70 may rock about the axes of the stub shafts 68 to insure engagement of the ocntact plates 70 with their mating pairs of contacts 24 and 33.

It will be apparent from inspection of Fig. 6 that the bracket 51 is narrow relative to the lengths of the contact plates 70 and their carriers 57, and hence when incorporated in the complete thermostat assembly of Figs. 1 and 2 will freely fit in the space between the two contact arms 21 and between the two contact arms 31 (Fig. 1). As shown in Fig. 2, the two contact plates 70 are disposed between the pair of contacts 24 and the pair of contacts 33 with one contact plate engaging both contacts 24 in one snap position of the bimetal 40 and with the other contact plate engaging both contacts 33 in the other snap position of the birnetal.

Suitable mechanism is provided for adjusting the bimetal to change the temperatures at which the latter moves the contact assembly 50 to open one circuit and close the other and vice versa. As shown in Fig. 2, this mechanism may comprise an adjusting screw 75 threadedly mounted in the supporting wall 11, with a lock nut 76 to retain its adjustment. The degree of adjustment may be shown by an indicator 77 fixed on the screw 75, and cooperating indicia 78 stamped on the surface of the supporting wall 11.

It will be apparent from the above description that the present invention provides a thermostat which is extremely simple to connect and adjust, as all adjustment screws and terminal connections are readily accessible upon removal of any covering structure (not shown) which may be utilized. Further, the assembly is relatively inexpensive to manufacture inasmuch as most of the parts are molded of plastic or similar non-conductive material or are metal stampings, and a minimum of dissimilar parts are required.

In Fig. 7 there is shown a contact stop for use in the above-described thermostat when only one circuit is desired. In such situations the pair of contact arms 31 are omitted, and a pair of plastic or other non-electrically-v conductive material stops 80 is clamped between the thermostat assembly base 10 and the contact base 16, with the stop projections 81 received in openings 35 of the contact base and projections 82 received in the openings normally receiving the rivets 32. A knob 83 on each stop is positioned to replace the omitted contact 33, to limit downward movement of the contact assembly 50 when the single circuit is opened.

While the invention has been shown in several forms, it will be obvious to those skilled in the art that it is not so limited, but is susceptible of various other changes and modifications without departing from the spirit thereof.

What is claimed is:

1. A thermostat comprising an assembly base; a snapacting heat-responsive member including a first portion secured to said base and a second portion free to snap to a first position when its temperature reaches a predetermined first value and to snap to a second position when its temperature reaches a predetermined second value; a contact base of non-electrically-conductive material mounted on said assembly base; a first pair of contact arms carried by said contact base; a second pair of contact arms carried by said contact base; a contact carried by each of said contact arms; and a contact assembly including a non-electrically-conductive bracket secured to the second portion of the heat responsive member, a first contact plate aligned with the contacts of said first pair of contact arms, a second contact plate disposed in parallel spaced relation with respect to said first contact plate and aligned with the contacts of said second pair of contact arms, and non-electrically-conductive carrier structure supporting said contact plates in said bracket, whereby movement of said heat-responsive member second portion to said first position moves said first contact plate into bridging engagement with the contacts of said first pair of contact arms and said second contact plate out of bridging engagement with said second pair of contact arms, and movement of said heat responsive member second portion to said second position moves said first contact plate out of bridging engagement with the contacts of said first pair of contact arms and said second contact plate into bridging engagement with the contacts of said second pair of contact arms.

2. A thermostat comprising an assembly base; a snapacting heat-responsive member including a first portion secured to said base and a second portion free to snap to a first position when its temperature reaches a predetermined first value and to snap to a second position when its temperature reaches a predetermined second value; a contact base of non-electrically-conductive material mounted on said assembly base; a pair of contact arms carried by said contact base; a contact carried by each of said contact arms; a contact assembly including a non-electrically-conductive bracket secured to said second portion of the heat-responsive member, a contact plate aligned with said contacts, and carrier structure supporting said contact plate in said bracket, whereby movement of said heat responsive member second portion to said first position moves said contact plate into bridging engagement with said contacts and movement of said second portion to said second position moves said contact plate out of bridging engagement with said contacts; and non-electrically-conductive stop structure clamped between the contact base and the assembly base for limiting the movement of the contact assembly in contact-opening direction.

3. A thermostat comprising base structure; a snapacting heat-responsive member including a first portion secured to said base structure and a second portion free to snap to a first position when its temperature 7 reaches a predetermined first value and to snap to a second position when its temperature reaches a predetermined second value; first and second pairs of contacts carried by said base structure; and a contact assembly carried by and movable with the second portion of the heat-responsive member and comprising a U-shaped bracket of non-electrically-conductive material secured to said heat-responsive member second portion, a pair of identical contact plate carriers of non-electrically-conductive material mounted between the legs of said U-shaped bracket in face-to-face abutting relation, and first and second electrically-conductive contact plates supported by said pair of carriers in parallel spaced-apart relation with the first contact plate in bridging engagement with the first pair of contacts and the second contact plate out of bridging engagement with the second pair of contacts when the heat-responsive member second portion is in its first position, and withsaid first contact plate out of bridging engagement with said first pair of contacts and said second contact plate in bridging engagement with said second pair of contacts when said heat-responsive member second portion is in its second position.

4. For use in a thermostat of the type which includes a base structure, a pair of spaced contacts carried by the base structure, and a snap-acting heat-re sponsive member including a first portion secured to the base structure and a second portion free to snap between two positions in response to changes in its temperature to predetermined values; a contact assembly for attachment to the second portion of the heat-responsive member for movement therewith and comprising a U-shaped bracket, a pair of non-electricallyconductive carriers mounted in said bracket and each having a plurality of projections extending toward the other carrier, a contact plate of electrically-conductive material retained in said carriers by said projections, and means for retaining said carriers assembled in said bracket, said contact plate being in bridging engagement with said pair of spaced contacts when the heatresponsive member second portion is in its first position and being out of bridging engagement with said pair of spaced contacts when said heat-responsive member second portion is in its second position.

5. For use in a thermostat of the type which includes a base structure, a pair of spaced contacts carried by the base structure, and a snap-acting heat-responsive member including a first portion secured to the base structure and a second portion free to snap between two positions in response to changes in its temperature to predetermined values; a contact assembly adapted to be attached to the second portion of the heat-responsive member for movement therewith and comprising a U-shaped bracket of non-electrically-conductive material having openings through the free end portions of the legs thereof, a pair of identical contact plate carriers of non-electrically-conductive material disposed in face-to-face relation, each carrier having a plurality of projections extending toward the other carrier and having a stub shaft received in one of the bracket leg openings for supporting the carriers in the bracket, a pair of flat electrically-conductive contact plates supported by the pair of carriers in parallel spaced-apart relation with certain of the carrier projections disposed therebetween, and means retaining the carriers and contact plates assembled as a unit.

Clark et a1 July 15, 1947 Lee Oct. 21, 1952. 

